Why is sleep important?

Quality sleep helps maintain mood, productivity, memory, and cognitive performance. Research shows sleep deprivation is associated with increased mortality, Alzheimer’s, obesity, diabetes, cardiovascular disease, cancer, ulcerative colitis, and depression. Sleep plays a critical role in the normal function of the endocrine and immune systems. If you’re sleep deprived, you may have trouble fighting common infections.

Sleep deficiency has played a role in tragic accidents, such as Chernobyl, the Union Carbide chemical plant in Bhopal, Three Mile Island, and Exxon-Valdez. It’s estimated that driver sleepiness is a factor in about 100,000 car accidents each year, resulting in about 1,500 deaths.

Children and teens who are sleep deficient may have problems getting along with others. They may feel angry and impulsive, have mood swings, feel sad or depressed, or lack motivation. They also may have problems paying attention, and they may get lower grades and feel stressed.

Schools with healthier start times, on the other hand, see an increase in attendance, test scores, G.P.A.s, and health. In one study in which an intervention pushed start times later, it wasn’t just academic outcomes that improved; car crashes went down by as much as seventy per cent, and self-reported depression rates fell. Judith Owens, the director of the Center for Pediatric Sleep Disorders at Boston Children’s Hospital, has been studying the effects of school start times on the well-being of school-age kids. Even a delay of as little as half an hour, Owens has found, improves outcomes.

An American Academy of Sleep Medicine study found that lack of sleep directly impacts the causes of biological aging. Lead author Dr. Judith Carroll at the UCLA Cousins Center for Psychoneuroimmunology in Los Angeles studied 29 adults between the ages of 61 and 86 over a four-night period. Not only was sleep quality analyzed, but blood samples also were taken each morning to assess gene expression. The results showed that a single night of sleep troubles activated gene patterns consistent with faster aging.

Just as important as quantity of sleep, is getting the right mix of REM (rapid eye movement) and NREM (non-rapid eye movement) sleep. In normal sleep, REM and NREM sleep alternate throughout the night according to a predictable pattern referred to as the “sleep architecture.” REM sleep first occurs about 90 minutes after falling asleep and recurs about every 90 minutes. Babies can spend up to 50% of their sleep in the REM stage, compared to only about 20% for adults.

REM sleep in particular is needed for maintaining brain cells: “Brain cells are some of the few cells in our bodies that we retain throughout our lives,” says Charles Czeisler, the director of Harvard Medical School’s Division of Sleep Medicine. “We store our memories, and through their complicated architecture, they are difficult to replace.” Sleep is when toxins accumulated by the body get flushed out of the brain, such as beta-amyloid, a protein associated with Alzheimer’s.

If REM sleep is disturbed one night, our bodies don’t follow the normal sleep cycle progression the next night. Instead, we may slip directly into REM sleep and go through extended periods of REM until we “catch up” on this vital stage. Caffeinated beverages, nicotine, and alcohol can negatively impact REM sleep.

The National Sleep Foundation suggests setting a regular bedtime that allows for enough rest and natural awakening, without an alarm clock. Sleep research shows that adults need between seven to nine hours of sleep each night, teenagers need about 9.5 hours, and infants generally require around 16 hours per day.